Chracterization of strain and composition in InGaN films by photoreflection and Raman scattering

1.GaN中的应变和电输运参数：我们通过拉曼散射测量E_2声子模频率来评估GaN薄膜中的面内应变，我们还利用拉曼散射测量了n型GaN薄膜中的载流子浓度和迁移率以及空间分布。p型材料中的载流子浓度可以通过拉曼光谱中观察到的空穴价带间跃迁的强度来获得。GaN薄膜中六角组分到立方组分的空间分布：通过对GaN拉曼光谱特征的研究，我们估算了GaN薄膜中六方结构的比例和它们的空间分布。AlGaN和InGaN薄膜的成分：我们首次观察到了立方AlGaN薄膜的拉曼光谱，我们观察到了声子频率与Al含量的各种关系，我们还首次观察到了生长过程中无厚GaN缓冲层的六方InGaN薄膜的拉曼光谱。在In含量为0-7%的范围内，我们观察到了E_2声子模频率的线性关系。这些结果将用于成分表征。我们通过吸收和光反射测量估算了带隙能量。根据测量结果估算了In的含量，并与声子频率的拉曼数据进行了比较。用于拉曼微观探测和光反射测量的紫外光激发系统：我们研制了一种用于拉曼微观探测和光反射测量的紫外光激发系统，并通过测量Si和GaN在共振拉曼条件下的拉曼光谱来测试系统的性能。

1. Strain and electric transport parameters in GaN :We have evaluated in-plane strains in GaN films from a measurement of the E2-phonon mode frequency by Raman scattering.We have also evaluated carrier concentration and mobility in n-type GaN films together with the spatial distribution by Raman scattering.Carrier concentration in p-type materials can be obtained from the intensity of inter-valence band transition of holes observed in Raman spectra.2. Spatial distribution of hexagona1- to cubic-components in GaN films :We have evaluated the ration and their spatial distribution by focusing on a characteristic feature in GaN Raman spectra.3. Composition in AIGaN and InGaN films :We have observed Raman spectra of cubic-AIGaN films for the first time for the whole range of Al composition (0-100%).We have observed various dependences of phonon frequencies on the Al content, and showed a good agreement with a theoretical model.We have also observed for the first time Raman spectra of hexagonal-InGaN films without thick GaN buffer layers in the growth process.We have observed a linear relation of the E2-phonon mode frequency on the In content of 0-7%.These results will be usable for composition characterizations.We have evaluated the bandgap energy by absorption and photoreflection measurements.The In contents were evaluated from the results and compared with Raman data on phonon frequencies.4. UV-excitation system for Raman microprobing and photo-reflection measurements :We have developed a UV-excitation system for Raman microprobing and photo-reflection measurements.We have tested the system performance by measuring Raman spectra of Si and GaN in the resonant Raman condition.